The present invention pertains to devices, systems, and methods useful in treating an eye. Certain embodiments of the devices, systems, and methods disclosed herein may be particularly suitable in maintaining separation of an anterior capsule and a posterior capsule of an evacuated lens capsule of an eye. Certain embodiments of the devices, systems, and methods disclosed herein may be particularly suitable for reducing scarring in the visual field of an eye having a capsulorhexis.
The human eye has a transparent crystalline lens structure, which is located immediately behind the iris. This crystalline lens is formed from epithelial cells, and the cytoplasm of these cells makes up the transparent substance of the lens. The crystalline lens may be described as having four layers, which layers (identified from the surface of the crystalline lens to the center) are the capsule, subcapsular epithelium, cortex, and nucleus. The lens capsule is a clear, membrane-like structure that is quite elastic, a quality that keeps it under constant tension. As a result, the lens naturally tends towards a rounder or more globular configuration, a shape it must assume for the eye to focus at a near distance. The lens is held in place by slender, strong suspensory ligaments (also known as zonules), which attach at one end to the lens capsule and at the other end to the ciliary processes of the circular ciliary body around the inside of the eye.
The human eye naturally has the ability to focus on both near and far objects by adjusting the shape of the crystalline lens. This adjustment is referred to as “accommodation,” and is associated with a concurrent constriction of the pupil. Accommodation occurs with the relaxation and contraction of the ciliary muscle in the ciliary body, which increases or decreases tension on the suspensory ligaments, which in turn acts on the lens capsule around its equator to cause the entire lens to flatten (become less convex) or round (become more convex). When ciliary muscles relax, the lens becomes less convex, and light from more distant objects is focused on the retina. When ciliary muscles contract, the lens becomes more convex and light from closer objects is focused on the retina.
The maximum amount that the crystalline lens can change shape is called the “amplitude of accommodation.” The amplitude of accommodation is very high when young, but decreases with age. This normal condition is known as “presbyopia,” and may be due both to a lessening of flexibility of the crystalline lens and to a generalized weakening of the ciliary muscle that causes the lens to accommodate.
Furthermore, the crystalline lens often develops a cataract, which is an opaque region or clouding of the lens. This condition leads to widespread application of techniques to remove the crystalline lens. One common procedure, called “extracapsular” cataract extraction, is frequently used to treat a cataract. In this procedure, an opening is made in the front of the lens capsule. Through this opening, the lens nucleus is removed, either as a whole or by dissolving it into tiny pieces and vacuuming out the pieces, a procedure called “phacoemulsification.” Next, the lens cortex also is sucked out, leaving the lens capsule in place, at which point a conventional intra-ocular lens (IOL) often is inserted into the lens capsule. When a conventional (monofocal) IOL is implanted, the accommodating ability, if any, is very limited. Accordingly, the wearer or user of the conventional IOL may use corrective spectacles as a useful aid in vision. Multi-focal IOL's without accommodating movement have been used to provide near and far vision correction.
A variety of attempts have been made to provide IOL's with accommodating movement in the eye. One such device is the CRYSTALENS, which was approved for use in the United States in November, 2003. (Another accommodating lens has been approved for use in Europe.) The CRYSTALENS has a single optic attached to hinged haptics. The optic is vaulted in the posterior position against the posterior capsule. Operation of the ciliary muscle increases the pressure in the vitreous humor, moving the optic in an anterior direction, thereby increasing the power of the optic. Relaxation of the ciliary muscle allows the lens to move backward. The forward and backward motion simulates natural lens accommodation. However, the amount of accommodation is limited. The CRYSTALENS normally includes a relatively small optic zone to enhance optic movement, but thereby this increases the chances of nighttime glare and halos.
Likewise, accommodation may be achieved by using optics made of two different materials to enhance the accommodation achievable in the eye in response to normal accommodative stimuli, as disclosed in U.S. Pat. No. 6,645,246.
The creation of an opening in the front of the lens capsule (a “capsulorhexis,” such as may be formed during refractive surgery, for example) may give rise to a number of subsequent problems. For example, the capsulorhexis may heal in a manner that may create scar tissue in the field of vision of the eye, which may impair vision through the eye after such healing of the capsulorhexis. As another example, the scar tissue may form during the healing process in a fashion that may displace objects implanted in the lens (e.g., intraocular lens devices, and the like, that may have been implanted during a surgical operation in which the capsulorhexis was created). Such displacement often is undesirable because, inter alia, it may move the implanted object partially, or entirely, outside of the visual axis. Such a situation often is referred to as “decentration,” and it may cause, inter alia, blurred vision, double vision, and the like.
Additionally, operations that involve the evacuation of the lens capsule also may be problematic, because, inter alia, the lens capsule may deform after its evacuation, and may fail to attain its original shape even after subsequent placement of a device within the lens capsule. Reduced eye volume may lead to a variety of problems, including, inter alia, retinal detachment. Furthermore, an evacuated lens capsule may impair the accommodation achievable in the eye.